URH 20W to 100W UL Series Metal Clad Resistor
Wire wound resistive element in aluminium-housed, cement-moulded construction
UL certified chassis-mount series spanning four power tiers: 20W, 30W/50W, 70W and 100W on heatsink
URH25C: 20W on heatsink, 8W in free air — resistance range 0.27Ω to 25kΩ inductive, 0.1Ω to 10kΩ non-inductive
URH50C: 30W on standard heatsink, 50W on large heatsink, 10W in free air — resistance range 0.68Ω to 50kΩ inductive, 0.2Ω to 20kΩ non-inductive
URH70C: 70W on heatsink, 20W in free air — resistance range 8Ω to 1.3kΩ inductive, 4Ω to 100Ω non-inductive
URH100C: 100W on heatsink, 30W in free air — resistance range 10Ω to 1.63kΩ inductive, 5Ω to 117Ω non-inductive
Tolerance options ±1% (F), ±2% (G) and ±5% (J)
TCR options ±60, ±70 and ±110ppm/°C (URH25C/50C); ±260ppm/°C (URH70C/100C)
Operating temperature range −55°C to +130°C (URH25C/50C) and −55°C to +200°C (URH70C/100C)
Dielectric withstanding voltage AC 1500V for 1 minute; AC 2000V option available
Insulation resistance 20MΩ minimum
Standard and non-inductive winding options across the series
100% RoHS compliant
What is the URH 20W to 100W UL Metal Clad Resistor?
The URH series is a UL-certified family of aluminium-housed, cement-moulded, metal clad wire wound resistors designed for chassis-mount installation in high-power industrial and power electronics applications. The series spans four models — URH25C, URH50C, URH70C and URH100C — covering continuous power ratings from 20W up to 100W on an appropriate heatsink, and from 8W to 30W in free air. The aluminium housing provides mechanical rigidity and efficient thermal conduction to the chassis or external heatsink, enabling direct heat dissipation without additional thermal interface hardware. High stability at conventional power ratings is a stated design objective of the series, making it well suited to applications requiring consistent resistance values over long service intervals.
The URH25C and URH50C share a common set of TCR and tolerance characteristics, with TCR values of ±110ppm/°C for resistance values below 1Ω, ±70ppm/°C from 1Ω to 19.6Ω, and ±60ppm/°C from 20Ω upward (measured at −55°C, +25°C and +250°C). Their resistance ranges differ in proportion to their power ratings: the URH25C covers 0.27Ω to 25kΩ in the inductive winding and 0.1Ω to 10kΩ in the non-inductive variant, while the URH50C extends to 0.68Ω–50kΩ and 0.2Ω–20kΩ respectively. The URH70C and URH100C target higher power densities with wire-terminated outputs and a TCR of ±260ppm/°C, covering resistance ranges appropriate to higher-current, lower-impedance load conditions. Their operating temperature ceiling rises to +200°C, reflecting the greater thermal demands of their power ratings. Across all four models, tolerance options of ±1%, ±2% and ±5% are offered.
The URH series is available in standard inductive and non-inductive winding configurations throughout. Non-inductive winding eliminates the parasitic inductance inherent in conventional wire wound construction, making the non-inductive variants suitable for snubber, damping and switching circuits where inductive reactance at operating frequencies would otherwise compromise circuit performance. The dielectric withstanding voltage of AC 1500V for one minute, with an AC 2000V option on request, confirms suitability for industrial line-voltage environments. Short-time overload ratings are five times rated power for five seconds on the URH25C and URH50C, with load life endurance tested to 1000 hours at rated power on a 1.5-hours-on, 30-minutes-off cycle. The UL certification distinguishes the URH series within the broader RARA metal clad range, supporting use in applications and markets where UL recognition is a procurement or regulatory requirement.
URH 20W to 100W UL Metal Clad Resistor Specifications
A practical overview for engineers and procurement teams evaluating resistive solutions.
Model: URH
Resistor type: Metal clad resistor
Description: UL Aluminum housed, chassis mounted
Power Rating: 20W-100W
Resistance (Ω): 0.1~50k
Tolerance (%): ±1, ±2, ±5
TCR (ppm/C): 30, 50, 100, 200
Applications of the URH 20W to 100W UL Metal Clad Resistor
Where RARA metal clad resistors are deployed in the field.
Motor drive and variable-speed drive circuits — dynamic braking and DC bus discharge resistors
Power converter snubber networks — non-inductive winding for IGBT and GTO transient energy absorption
Electric power conversion systems — chassis-mounted load and protection resistors
Industrial power supplies — current limiting, soft-start and inrush protection
UPS and power conditioning equipment — load banks and battery discharge networks
Inverter and converter gate drive circuits — series damping and parallel protection resistors
High-power switching circuits — non-inductive variant for filter and snubber stages
UL-certified installations — panel and cabinet wiring where UL recognition is required
Test and measurement equipment — precision load resistors across tolerance grades
Industrial automation and control panels — compact chassis-mounted high-power dissipation
Renewable energy systems — dump load, crowbar and overvoltage protection assemblies
Automotive and transportation power electronics — chassis-mount resistors in thermally demanding environments
Related Products of the URH 20W to 100W UL Metal Clad Resistor
Model: RH10C
Resistor type: Metal clad resistor
Description: Metal clad cement encased
Power Rating: 10W
Resistance (Ω): 0.1~6k
Tolerance (%): ±0.5, ±1, ±2, ±5
TCR (ppm/C): 260 Max.
Model: RH, FRH
Resistor type: Metal clad resistor
Description: Aluminum housed, chassis mounted
Power Rating: 15W, 20W, 50W
Resistance (Ω): 0.1~2M
Tolerance (%): ±0.1, ±0.5, ±1, ±5, ±10
TCR (ppm/C): 40, 50, 100, 200
Model: IRBT
Resistor type: Metal clad resistor
Description: Automotive
Power Rating: 60W
Resistance (Ω): 1~1k
Tolerance (%): ±5, ±10
TCR (ppm/C): 260 Max.
Model: IRS
Resistor type: Metal clad resistor
Description: Slim profile, aluminum housed, chassis mounted
Power Rating: 30W, 50W
Resistance (Ω): 1~500
Tolerance (%): ±0.5, ±1, ±2, ±5, ±10
TCR (ppm/C): 260 Max.
Why Choose RARA Metal Clad Resistors
What sets RARA apart for engineers and procurement managers in industrial and automotive markets.
01
Automotive Qualified
AEC-Q200 tested models and IATF 16949 certification for EV and automotive powertrain applications. Trusted by GM Korea, Tesla, and Proterra.
02
STEP Files Included
3D STEP files available for core models, supporting ECAD/MCAD integration and thermal management simulation in your design workflow.
03
Wide Power Range
A single product family spanning 10W to 8.5kW means you can source across a project from one qualified, certified supplier.
04
Global Track Record
Deployed by Siemens, Rockwell, Toshiba, Schneider Electric, LG, and Hanwha — a customer list built on decades of consistent performance.
